1. Field of the Invention
A submersible pump is disclosed having a cooling jacket for cooling the pump and the motor when a liquid medium is pumped through the jacket. To enable the pump to continue to function without overheating in the absence of a liquid medium, a partition is provided within the jacket to cause air to circulate and transfer heat from hot portions to cool portions of the jacket.
2. Description of the Prior Art
A submersible pump is able to work above as well as in the pumped medium. Especially by submersible drainage pumps, which are intended for pumping water that is comparatively free from pollution, it is common to let the pumped water pass around the driving motor of the pump on its way towards the outlet pipe. An electric motor needs cooling and a suitable way to bring this about is to arrange a housing (jacket) around the motor and let the water pass this jacket on its way to the outlet. As new water is brought in continuously the cooling will be very good.
However, a submersible drainage pump must be able to run dry, which means that the pump must be able to run during a long time without getting overheated even if the water is gone. As it often happens that the pump outlet is closed because of the fact that the outlet pipe does not end in the open air but under a water surface for instance, the jacket which surrounds the motor, then will contain air which more or less is stagnant and therefore the thermal dissipation is very poor. That situation involves great risks for overheating in a pump motor which normally would get enough cooling.